Hyperbranched polymers are polymers whose structures resemble those of dendrimers. These polymers have recently attracted attention since they can be readily synthesized compared to dendrimers although they have similar chemical and physical properties to those of dendrimers.
Regarding hyperbranched polymers, there hitherto have been a few reports on hyperbranched polymers with polystyrene structures and it is known that it is possible to synthesize desired multi-branched polymers by providing a monomer with a reaction initiation point (please refer to Macromolecules, 29, 1079 (1996), J. Polym. Sci., Part A:
Polym. Chem., 36, 955 (1998)).
However, it has not been necessarily easy to control the molecular weights or degrees of dispersion of the hyperbranched polymers described in these documents and especially in the case where the degree of branching was high, only polymers with a high degree of dispersion could be obtained.
Accordingly, there has been a demand for the development of hyperbranched polymers with excellent physical properties by controlling the proportion of branching, molecular weights, shapes, and so forth.
Moreover, there is a report on a method of synthesizing hyperbranched polyacrylates using an atom transfer radical polymerization (ATRP) method illustrating living radical polymerization of AB type acrylic monomers (please refer to Macromolecules, 30, 5192 (1997)). Although hyperbranched polymers with the AB*type acrylic monomers as the polymerization-initiation sites have been provided, the structures of the obtained hyperbranched polymers are not symmetric and the polymers are not those with so-called star polymer properties. Information on AB2 type acrylic monomers has not been disclosed.